Co3O4 + CeO2/SiO2 Catalysts for n-Hexane and CO Oxidation

Abstract

Two-component Co-Ce samples deposited onto SiO 2 have been prepared, characterized and tested in the reaction of complete n-hexane and CO oxidation. It was established that cerium enhanced the catalytic activity of cobalt in the reaction of n-hexane oxidation, although this depended on the sequence of cobalt and cerium introduction. Co-impregnation of Co and Ce resulted in a close interaction between Co 3 O 4 and CeO 2 leading to more surface oxygen species available and, therefore, a better reactivity.

Catalytic oxidation of volatile organic compounds (n-hexane, benzene, toluene, o-xylene) promoted by cobalt catalysts supported on γ-Al2O3-CeO2

“…It is important to note that the greater reducibility of Co 10 /γ-Al 2 O 3 -CeO 2 did not translate into higher VOC oxidation activity. However, other factors to be considered are the presence of active sites, such as Co 2+ and Co 3+ ions, strong interaction between the oxide phases and oxygen vacancies on the Co 20 /γ-Al 2 O 3 -CeO 2 catalyst surface as confirmed by the characterization results discussed above, which is related to the oxidation of hydrocarbons (Cordatos et al, 1996;Lefez et al, 1996;Putna et al, 1999;Volta and Portefaix, 1985;Todorova et al, 2009;Todorova et al, 2011). The cobalt enrichment on the catalyst surface (as evidenced by the XPS data) may have contributed to the higher activity observed for the Co 20 /γ-Al 2 O 3 -CeO 2 catalyst, since cobalt is a very active species in oxidation reactions.…”

“…The higher oxygen mobility benefits the oxygen species migration across the catalyst structure, resulting in higher oxidation activity (Song et al, 2009). It has been shown that the reduction in cerium oxide (Ce +4 /Ce +3 ) is not due to a direct release of oxygen into the gas phase, but rather to the interaction which occurs between the surface of the catalyst and the hydrocarbon (Putna et al, 1999;Suresh et al, 2012;Todorova et al, 2009;Todorova et al, 2012). These reactions are driven by the increased capacity for the spontaneous release of oxygen from the Co 3 O 4 /CeO 2 system, even in the absence of a reducing agent.…”

“…It is well known that the oxidation of hydrocarbons promoted by solid oxide catalysts (including cerium oxide catalysts) can proceed via the Mars and van Krevelen mechanism in which the key steps are the supply of oxygen by the reducible oxide, the introduction of the oxygen species from the lattice oxide into the substrate molecule, and the re-oxidation of the reduced solid by the oxygen-containing gaseous phase, the rate-determining step of the reaction (Menezo et al, 1993;Todorova et al, 2012). According to Todorova et al (2009), the oxygen storage capacity of cerium oxide is associated with a fast Ce 4+ /Ce 3+ redox process, making more oxygen available for the oxidation process. The oxygen migration on the catalyst surface is important in oxidation reactions, where the oxidation-reduction cycles determine the catalytic activity.…”

Study of Oxygen Reactivity in La1−x Sr x CoO3−δ Perovskites for Total Oxidation of Toluene

“…For these reasons, other alternatives have been studied during the past years. Among them, it is worth mentioning the use of photocatalysts [9] and different mixed oxides containing transition metals [2,10,11].…”

Effect of CeO2 on the properties of the Pd/Co3O4/cordierite catalyst in the conversion of CO, NO, and hydrocarbons

“…Rare earth oxide (REO) doping may increase the activity of transition metal oxide catalysts. Considerable interest has been found in systems containing cobalt oxide (Co 3 O 4 ) with REO (CeO 2 , La 2 O 3 ), which display high activity in the oxidation of CO and hydrocarbons and the reduction of NO and may be used for the purification of automobile exhaust gases [1, [4][5][6]. The high catalytic activity of mixtures of Co 3 O 4 and CeO 2 is attributed to the formation of Co-O-Ce surface clusters during preparation [1,7].…”